Piston expander



Dec. 16, 1947. M SIPE 2,432,687

PISTON EXPANDER Filed Aug. 8, 1946 f" 3 1X I H mmvrox. MART/N t. 51 15.

A TTORNE Y.

Patented Dec. 16, 1947 UNITED STATES PATENT ()FFICE PISTON EXPANDERMartin E. Sipe, Denver, Colo.

Application August 8, 1946, Serial No. 689,121

3 Claims. 1

This invention relates to improvements in means for expanding a splitpiston skirt to compensate for Wear and eliminate piston slap, excessoil consumption, blow by and other objections due to excess wear.

It is well known that split skirt pistons, especially those made fromaluminum and aluminum alloys wear rapidly and soon develop pistonslapfiexcessive leakage of oil and gas, etc.

In order to automatically compensate for such weanvarious specificallydifferent devices have been invented for exerting a constant expandngforce on the piston skirts. Piston skirt expanders are, as a rule, madefrom rather thin steel that is bent into the desired shape and thenhardened and tempered.

Piston skirt expanders must be constructed in such a manner that theyare held in deformed position by suitable means in which condition theymay be introduced into the piston'after which the restraining means isremoved allowing the device to expand into engagement with the innersurface of the piston. skirt.

One specific form of piston skirt expander is shown in my pendingapplication Serial No. 642,- 287 filed January 19, 1946, now Patent No.2,418,053.

It is the object of this invention to produce a piston skirt expander ofthe general shape shown in the above identified application, which shallbe so constructed that it can be more readily manufactured and assembledand in which the restrainin means can be more readily renderedinoperative.

Having thus described the invention in a general way and some of itsobjects, the invention will now be described in detail and for thispurpose reference will be had to the accompanying drawing in which theinvention has been illustrated, and in which:

Figure 1 is an end view of a split skirt piston, looking through planel--i in Figure 2 and shows the expander in position and before it hasbeen released;

Figure 2 is a side elevation of a piston, partly broken away to show anend view of the expander;

Figure 3 is a section taken on line 3-3, Figure 2;

Figure 4 is a plan view of the expander; and

Figure 5 is a perspective view of one-half of the expander.

In the drawing reference numeral 5 designates an ordinary automobilepiston of the split skirt numeral 6 and the cut in the skirt wall byreference numeral 1. The specific type of piston illustrated hasopenings 8 at opposite sides and is provided with aligned bearings 9 forthe piston pin ill. The piston pin bosses have inward extensions whichhave been designated by reference numerals l The expander is positionedbetween the bosses l I in the manner shown in Figure 1 and will now bedescribed in detail.

The expander consists of two identical pieces like the one shown inperspective in Figure 5, each half of the expander has a straight centerportion i2 that is provided with an opening l3 through which th pistonpin may pass. At the ends of the straight portion i2, the material isbent inwardly at an angle of substantially degrees forming inclinedwalls l4 that terminate in out-' wardly convex reverse curves l5 thatagain terminate in reversely extending end portions I B which aretapered as shown in Figure 4 and have narrow ends I! that lap thestraight portion l2 and are bent sothat they are parallel with thestraight portions when in contact therewith. Ends it normally occupypositions like that designated by reference numerals [8 shown by dot--ted lines in Figures land 4 and must be forced into the full linepositions by means of suitable bending tools which have not been shownin the drawing. After ends it have been forced into the full lineposition shown in Figure 5, ends I1 are spot-welded to the straightsides I2 and in Figure 4 the welding electrodes have been shown bybroken lines. The spotweld holds the ends IS in full line position untilit is broken by means of a suitable tool. In Figure 4 the piston skirthas been indicated by dotted lines and it will be seen that when theexpander is in full line position, some space is left between the endsof the expander and the inner surface of the skirt so as to permit theexpander to be freely inserted. After it has been inserted, thespotwelds are broken, as above intimated, and the curved ends is movedoutwardly into engagement with the inner surface of the skirt exertingon the piston skirt a strong expanding force that moves the partsoutwardly to compensate for wear.

In order to facilitate the distribution and also the insertion of theexpanders, each expander part is provided with arms i9 that overlap asshown in Figure l and which are spotwelded in overlapped position. Theinterconnection between arms l9 facilitates the handling of the expanderand its insertion into the piston. After the expander is type. The skirthas been designated by reference, is; in posit o a s 9 form noparticular useful function and the connection between them may then bebroken, if desired.

It will be observed that the expander that forms the subject of thisinvention is of a very similar construction to the one described andclaimed in the above identified application and patent. The main, andalmost the only distinction between the two structures, is that in theapplication above identified, the resilient ends l6 are secured to theremainder of the expanders by means of a releasable mechanical latchsuch as a hook, whereas, in the present embodiment, the ends are securedto the straight portions by means of spotweld.

In order to make it practical to spotweld the parts in the manner shownin the drawing, the ends H must be so bent or curved that they will beparallel with the surface to which they are spotwelded. If the parts arenot so related as to effect this, very powerful strains are set up thatwill break the spotweld. In the embodiment i1- lustrated, ends lloverlap straight sides l2, but it is possible and may, at times, bepreferable to spotweld the ends of members it to the outer surface ofthe inclined walls [4, in which case ends I! must be bent in such awayas to make them parallel with the surface to which they are to bespotwelded, and such a construction has been indicated by dotted linesin Figure 4.

The construction described above has several advantages over theconstruction shown in the application above identified, some of whichpertaln to the manufacture of the expander making it possible to efiectthe entire manufacture and assembly by means of suitable tools andanother advantage derived from this is that the ends Hi can be releasedby means of a screwdriver or chisel with less effort than necessary torelease the interconnection employing a hook.

The construction above described can also be made with simpler andcheaper dies than a construction employing a hook interconnection.

In the above description the invention has been explained in connectionwith a split skirt piston. Some pistons do not have split skirts, buthave very thin skirts instead and the expander, when used with such thinskirts, deforms the piston forcing it out of round and efiects the samere* sult as with a split piston.

Having described the invention what is claimed as new is:

1. A piston skirt expander of generally elongated hexagon shape,provided at each end with outwardly and rearwardly curved resilientportions lying wholly on the outside of the hexagon, said rearwardlycurved portions being biased with their ends away from the outside ofthe hexagon but movable into contact therewith, in response to asufficient force, the ends being shaped to present a flat surfaceparallel with the surface of the hexagon surface, the ends beingconnected with the hexagon by a spotweld of suilicient strength toresist the force exerted by the resiliency of the reversely curvedportions.

A piston skirt expander of generally elongated hexagon shape, providedat each end with outwardly and rearwardly curved resilient portionslying wholly on the outside of the hexagon, said rearwardly curvedportions being biased with their ends away from the outside of thehexagon but movable into contact therewith in response to a suflicientforce, the ends being shaped to lap the central flat sides of thehexagon and to present a flat surface parallel therewith, the ends beingconnected with the central fiat portion by a spotweld of sufficientstrength to resist the force exerted by the rearwardly bent resilientends.

3. A piston skirt expander of generally elongated hexagon shape,provided at each end with outwardly and rearwardly curved resilientportions lying wholly on the outsidt of the hexagon, said rearwardlycurved portions being biased With their ends away from the outside ofthe hexagon but movable into contact therewith in response to asuflicient force, the ends being shaped to lap the central fiat sides ofthe hexagon and to be moved into parallelism therewith, the ends beingconnected with the central flat portion by a spotweld of sufficientstrength to resist the force exerted by the rearwardly bent resilientends.

MARTIN E. SIPE.

